Luffy's punches seemed really light this time. Surely a scientist like Caesar shouldn't be the most heavyweight fighter around. It makes sense he knows his own abilities through and through, but why can he take punches without flinching like some old pirate or marine? Especially punches boosted by haki.

I was severely underestimating Monet if she thinks she can stand against Luffy. Although perhaps it's precisely because Luffy couldn't beat Caesar in a timely manner that Monet realised Luffy isn't that tough and decided to intervene.

In any case, based on this, Luffy isn't ready for the New World.